1. Technical Field
The present invention relates generally to a method, system, and computer program product for managing the use of electrical power in a data processing environment. More particularly, the present invention relates to a method, system, and computer program product for system-wide power conservation using memory cache.
2. Description of the Related Art
Memory in a data processing system includes one or more solid-state memory devices, such as a Dual Inline Memory Module (DIMM). Not only the processors or processing cores, but also many other components and subsystems in the data processing system need access to the memory.
Access to the memory in a direct way is slower than acceptable in most cases. A cache memory (cache) is a faster but smaller memory device used for speeding up access to the most used or recently used data from the memory.
Various types of caches are presently in use. A particular type of cache is configured and located in a certain way depending on the nature of the use expected from that cache. For example, certain caches, such as level-1 (L1), level-2 (L2), and level-3 (L3) caches known as CPU-caches, and are used by processors for reading and writing data during instruction execution. L1, L2, and L3 caches are fast but small memory devices, typically formed on the same chip as the processor core for fast operation in close proximity to the processor.
Other levels of caches are not exclusively for use by the processor only. For example, a level-4 (L4) cache is a cache that is accessible to any subsystem in a data processing system, and any subsystem can read or write the memory via L4 cache. As with other caches, L4 cache includes faster devices but of smaller capacity as compared to the memory, and expedites access to recently used or frequently used data in the memory. As an example, a networking subsystem, e.g., comprising a network adapter, or an input/output (I/O) subsystem, e.g., comprising an I/O controller, or a partition management subsystem, e.g., in a multi-partitioned data processing system, can each access the memory via an L4 cache in a given configuration.
Electronic components, including memory devices used for main memory or cache memory, consume electrical power. A system-wide power saving condition is a condition that indicates that the power consumption of the data processing system as a whole has to be reduced.